A ring-spinning machine generally comprises, on each side of the machine frame, a row of spindles each of which can be considered to represent a station at which yarn, usually fed from a drafting frame, is twisted and wound upon a core sleeve on the spindle. In the process, a yarn balloon is formed around the spindle. The apparatus can then include a ring surrounding the spindle and usually on a ring rail which can move relative to the spindle or with respect to which the spindle can move relatively in an axial direction so that the yarn of the bobbin is distributed over the length of the core sleeve. At the lower end of the balloon, therefore, the yarn can pass through a traveler riding on this ring. The balloon is formed as a result of centrifugal forces on the yarn and the yarn tension, which is in part determined by the centrifugal forces, can contribute to thread breakage.
To limit the expansion of the balloon, a balloon confining or constricting ring may be provided around the spindle as well and in the ring spinning of a yarn, measures to limit the balloon can contribute to a reduction in the rate of thread breakage and thus to an improvement in yarn quality.
Earlier systems tended to use traveling thread-guide eyes or, as described in DE-OS 21 54 446, for example, thread guides which are fixedly mounted on the ring-spinning machine or even thread guides which can be upwardly swingable (DE-OS 16 85 673). In the latter construction, the pivot axis of the thread guide is fixed with respect to the ring-spinning machine while the thread-guide eye itself can be upwardly swingable in combination with the balloon-constricting ring. Other swingably-mounted thread guides are described in Japanese open applications SHO-60-155739 and SHO-60-146022.
In the British patent 948,537 an articulated mounting of the thread guide on a bar is described, the mounting allowing the upward swing of the thread guide for a bobbin-change operation.
A thread-guide eye can be embedded in a piezoelectric elastic element (EP 0 046 810 B1) enabling the detection of yarn breaks as a result of characteristic oscillations generated by the passage of the yarn through the guide. In U.S. Pat. No. 3,269,104, a spring-mounted thread-guide eye is described which allows the holder to be shiftable in a longitudinal slot or hole.
All of these systems have been proposed for spindles onto which the yarn is deposited only after passing through the traveler.
It has been found, however, that for effective limitation of the development of a yarn balloon, it can be advantageous to provide a headpiece for the spindle, i.e. to mount on the spindle, an element which engages in one or more turns the yarn so that the yarn balloon is formed between the headpiece and the traveler before the yarn is deposited on the core sleeve. Such a headpiece, which is fitted onto the top of the spindle, has a configuration, e.g. that of a finger, which allows the yarn to wind thereon in one or more loops.
The service person for such a machine can press the thread guide down sufficiently that the yarn will wind around the headpiece on the spindle. Because of the more or less considerable force which can develop, a forcible connection between the thread guide and any mounting element can become dislocated.
After a certain period of operation and multiple depressions of the thread guide, significant variation can occur between the positions of the thread-guide eyes and respective spindle headpieces for the machine to vary the tension state in the respective spinning triangles, yarn balloons and the winding zones for the various stations. As a consequence, there is a significant quality variation in the spun yarn from bobbin to bobbin and station to station along the machine. For the purposes of this description, the spinning triangle will be understood to be the region between the last pair of rolls of the drafting frame, the thread-guide eye and the headpiece of the spindle. It is in this region that the spinning of the yarn is most pronounced. The balloon zone will be understood to be that region between the headpiece of the spindle and the traveler or ring, and the winding zone, that region between the traveler or the ring and the point at which the yarn is deposited upon the core sleeve.